Synthesis and characterization of conducting self-assembled polyaniline nanotubes/zeolite nanocomposite

Self-assembled conducting, paramagnetic polyaniline nanotubes have been synthesized by the oxidative polymerization of aniline with ammonium peroxydisulfate in aqueous medium in the presence of zeolite HZSM-5, without added acid. The influence of initial zeolite/aniline weight ratio on the conductivity, molecular and supramolecular structure, paramagnetic characteristics, thermal stability, and specific surface area of poly aniline/zeolite composites was studied. The conducting (∼10-2S cm-1), semiconducting (3 × 10-5 S cm-1), and nonconducting (5 × 10-9 S cm-1) composites are produced using the zeolite/aniline weight ratios 1, 5, and 10, respectively. The coexistence of polyaniline nanotubes, which have a typical outer diameter of 70-170 nm and an inner diameter of 5-50 nm, accompanied by nanorods with a diameter of 60-100 nm and polyaniline/zeolite mesoporous aggregates, distinct from the morphology of mieroporous zeolite HZSM-5, was proved in the conducting nanocomposite by scanning and transmission electron microscopies. FTIR spectroscopy confirmed the presence of polyaniline in the form of conducting emeraldine salt and suggested significant interaction of polyaniline with zeolite. The evolution of molecular and supramolecular structure of polyaniline in the presence of zeolite was discussed

Synthesis and characterization of self-assembled polyaniline nanotubes/silica nanocomposites

Self-assembled semiconducting, paramagnetic polyaniline nanotubes have been synthesized by the oxidative polymerization of aniline with ammonium peroxydisulfate in aqueous medium in the presence of colloidal silica particles of an average diameter ∼12 nm, without added acid. The electrical conductivity of polyaniline nanotubes/silica nanocomposites is in the range (3.3-4.0) × 10-3 S cm-1. The presence of paramagnetic polaronic emeraldine salt form of polyaniline and phenazine units in nanocomposites was proved by FTIR, Raman, and EPR spectroscopies. The influence of the initial silica/aniline weight ratio on the morphology of polyaniline/silica nanocomposites was studied by scanning and transmission electron microscopies. Nano-composites synthesized by using the initial weight ratio silica/aniline ≤0.2 contain polyaniline nanotubes which have a typical outer diameter of 100-250 nm and an inner diameter of 10-80 nm, and nanorods with a diameter of 60-100 nm, accompanied with polyaniline/silica nanogranules, while the nanocomposite synthesized at weight ratio silica/aniline ∼2 contains polyaniline/silica nanogranules with an average diameter of 35-70 nm. The evolution of molecular and supramolecular structure of polyaniline in the presence of colloidal silica is discussed

Role of aniline oligomeric nanosheets in the formation of polyaniline nanotubes

We report the phenomenon of nanosheet rolling during typical aqueous polymerization and study its implications for the self-assembly of polyaniline nanotubes. Specifically, this is done through a detailed morphological and structural characterization of products obtained after 20 min, 1 h in falling pH experiments, and after 20 hat constant pH 2.5 during the oxidative polymerization of aniline with ammonium persulfate in the presence of alanine. The chemical Structure has been investigated by FTIR, UV-vis, solid-state C-13 and N-15 NMR, liquid NMR, and XRD. whereas the morphology was imaged using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The presence of self-assembled nanoflakes with different thicknesses ranging from tells to hundreds of nanometers is confirmed through SEM. TEM revealed the presence of very thin layers: nanosheets with sharp and well-defined edges. The presence of hydrogen bonds is confirmed by FTIR and is consistent with XRD results. The stacking of nanosheets and the formation of thicker flakes based on pi-pi electron interactions have been proposed on the basis of XRD experiments, where self-assembled layers made of cross-linked oxidized aniline structures stack on each other and are stabilized by hydrogen bonds and pi-pi interactions. In this way, hydrophobic cross-linked oligomers (formed at the beginning of the synthesis at higher pH) minimize their surface energy, self-assembling into well-ordered macromolecular structures. On the basis of the SEM and TEM images and the information obtained from other analytical techniques applied here, the presence of PANI nanotubes formed in the reaction carried Out at constant pH of 2.5 is confirmed. The role of the nanosheets in the formation of nanotubes is proposed